Quantitative Determination of Trace Metals and Sulphur Content in Nigerian Petroleum Products Using AAS and Gravimetric Analysis Technique
Chapter One
Aim and Objectives
This research work is aimed at determining and comparing the concentration of trace metals in different Nigerian petroleum products. This will contribute a lot in assessing the Nigerian petroleum products’, impact on the environment, technological processes, and economic potentiality.
The objectives of this research work are to:
- Identify the trace metals in the various petroleum product samples under study.
- Compare the results of the different digestion methods
- Compare the different petroleum product samples used in terms of trace metal concentration
CHAPTER TWO
MATERIALS AND METHODS
The various Nigerian petroleum products used in this research work are as follows: gasoline, kerosene, diesel oil, fuel oil, etc, and the trace metals and Sulphur content were analyzed using Atomic Absorption Spectroscopy (AAS) and Gravimetric techniques.
Materials
The materials used in this research work were Nigerian petroleum products ranging from;Petrol, Diesel, Kerosene, Fuel Oil, Low Pour Point Fuel Oil.
Methods
Three preparation methods were adopted for the five sample understudy thus; Total acid digestion, Ashing and Solvent dilution methods and also gravimetric method was adopted for the analysis of Sulphur content in the various petroleum products understudy
Sampling
Gasoline, kerosene, gas oil, LPFO and fuel oil used for the study were collected from Kaduna Refining and Petrochemical Company, using clean, dry bottles with firm screw tops.
Determination of Physicochemical properties of Nigerian petroleum products
Preliminary test was carried-out on various samples of petroleum products collected from the Nigerian petroleum refinery. The following parameters were tested and the results were recorded. Density, Specific Gravity, API Gravity, Flash point, Total Sulphur, Pour point, Flash point, Viscosity Kinematic Viscosity, Water content. The properties were determined by ASTM and IP methods as follows.
- Determination of Density, Specific Gravity and API gravity were determined using ASTM method; (Annual book, 1985; (a) I.P, 1987). The specific gravity determination involves weighing (W1) a known volume of a sample in a density bottle at certain temperature and weighing W2 an equal volume of water in the same density bottle at the same temperature. The specific gravity is the ratio of the two weights W1/W2. The API gravity of the sample was then calculated by using the equation ((a) I.P, 1987). API = 141.5/S.G – 131.5 Where S.G means Specific Gravity of the Sample.
Determination of Viscosity follows the IP method (Milner and Whiteside, (1986). This involves measuring the time of flow of the sample between two marked points on the Ostwald viscometer and calculating the viscosity by using the standard equation.
CHAPTER THREE
RESULTS AND DISCUSSION
The results were discussed in terms of effects of the sample preparation methods adopted, physicochemical parameters analyzed and concentration of trace metals determined.
Results
The Tables below presents the results of the preliminary analytical tests of the samples used.\
CHAPTER FOUR
CONCLUSIONS ANDRECOMMENDATIONS
The conclusion and recommendations of the quantitative determination of trace metals and sulphur content of Nigerian petroleum products using atomic absorption spectroscopy and gravimetric analysis techniques was presented below.
Conclusions
Some physico-chemical analyses of samples of Gasoline, Kerosene, Diesel Oil, Low Pour Point Oil and Residual fuel have been studied. The samples were also analyzed for trace elements. The results confirmed that Heavy distillates a fraction (Residual fuel and LPFO) contains trace metals higher than the distillates fraction (Automobile Gas Oil or Diesel) followed by intermediates (Dual Purpose Kerosene) and lights ends fractions(Premium Motor Sprit / Gasoline). The samples were analyzed by gravimetric and Atomic Absorption Spectrophotometry methods for sulphur and trace metals content.The experiment data indicated that, the total sulphur and other physicochemical properties increased from light ends, intermediates, distillates to heavy distillates fractions respectively and also the concentrations of the trace metals in the petroleum products follows the same trend i.e. from less viscous petroleum products (Gasoline, Kerosene and Diesel Fuel) to high viscous petroleum products sample (residual fuel and LPFO) .
This work showed that Nigerian petroleum products contain trace amount of cadmium, chromium, calcium, copper, iron, lead, nickel, manganese, vanadium, zinc, molybdenum, aluminium, magnesium, silicon, tin, cobalt, sodium and calcium. The presence or absence of some elements in Nigerian petroleum products may be link to the chemical and geological origin of its raw materials and also industrial process and the transportation method adopted. Hence the concentrations of trace and heavy elements in Nigerian petroleum products may reveal information on the environmental friendliness and quality of petroleum products and probably give an idea of the sources of these trace heavy metals in the petroleum industry. It was obvious from this study, the Nigerian petroleum products analyzed have low metal contents especially in petrol, kerosene and gas oil sample. However, even as this low levels, the metal contents of Nigerian petroleum products, and especially of iron, manganese, vanadium and aluminium etc is high enough to cause corrosion of turbines, distillation towers, etc (Oderinde,(1984).
Recommendations
In view of the results obtained from this study, the following recommendations are hereby made:
- Petroleum industries should provide enough fund for the Universities and supply latest analytical machines such as AAS,GC/MS and other very important analytical equipment to Universities/ Research Institutions as part of their public
- Since most of the sources of these metals are from the alloys used in constructing anti-corrosive pipes, processing equipment and storage materials,there is need for alternative pipes, processing equipments and storage materials constructed from such metallic alloys to be substituted with plastic or fiber material.
- Government should established emergency taskforce for the control of industrial and municipal discharge, especially for petroleum and petroleum products
- General public should be oriented and alerted on the danger of inhaling the exhaust of various transportation machines and avoid physical contact with these petroleum
- Storage tanks of the filling station must be inspected regularly, and specification of a standard storage tank must be
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